Extracellular Matrix Sheet Structures

ABSTRACT

A CO2 processed sheet structure comprising ECM derived from mammalian submucosa tissue, which can be formed into a pouch configured to encase a medical device.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 14/571,679, filed on Dec. 16, 2014, which is a division of U.S. application Ser. No. 13/896,424, filed on May 17, 2013, now U.S. Pat. No. 9,283,302, which is a continuation-in-part of U.S. application Ser. No. 13/573,566, filed on Sep. 24, 2012, now U.S. Pat. No. 9,066,993, which is a continuation-in-part of U.S. application Ser. No. 13/328,287, filed on Dec. 16, 2011, now U.S. Pat. No. 9,532,943, which claims the benefit of U.S. Provisional Application No. 61/425,172, filed on Dec. 20, 2010.

FIELD OF THE INVENTION

The present invention relates to implantable structures and devices. More particularly, the present invention relates to extracellular matrix (ECM) based sheet structures that can be configured to encase medical devices.

BACKGROUND OF THE INVENTION

As is well known in the art, treatment of various medical conditions commonly involves implantation of biological structures (e.g., prostheses), medical devices and/or insertion of medical instruments into a body. Illustrative is the implantation or deployment of heart valves to regulate the flow of blood through cardiovascular vessels, and pacemakers to control abnormal heart rhythms.

Implantable structures and medical devices; particularly, cardiovascular implants, have unique blood biocompatibility requirements to ensure that the structure or device is not rejected (as in the case of natural tissue materials for heart valves and grafts for heart transplants) or that adverse thrombogenic (clotting) or hemodynamic (blood flow) responses are avoided.

Several cardiovascular implants, such as heart valves, are formed from natural tissue. Illustrative are the heart valves disclosed in U.S. Pat. Nos. 6,719,788 and 5,480,424 to Cox. The disclosed bioprostheses can, however, be affected by gradual calcification, which can, and in many instances will, lead to the eventual stiffening and tearing of the implant.

Many non-bioprosthetic implants are, however, fabricated from various metals and polymeric materials, and other exotic materials, such as pyrolytic carbon-coated graphite.

For example, pacemakers, defibrillators, leads, and other similar cardiovascular implants are often fabricated from Ni—Co—Cr alloy, Co—Cr—Mo alloy, titanium, and Ti—6Al—4V alloy, stainless steel, and various biocompatible polymeric materials.

By way of further example, artificial heart valves are often fabricated from various combinations of nylon, silicone, titanium, Teflon™, polyacetal, graphite and pyrolytic carbon.

Further, artificial hearts and ventricular assist devices are often fabricated from various combinations of stainless steel, cobalt alloy, titanium, Ti—6Al—4V alloy, carbon fiber reinforced composites, polyurethanes, Biolon™, Hemothane™, Dacron™, polysulfone, and other thermoplastics.

Finally, catheters and guide wires are often fabricated from Co—Ni or stainless steel wire. In many instances, the wire is encased in a polymeric material.

As is well known in the art, several major problems are often encountered when a medical device (or other device, e.g., tracking apparatus) fabricated from one of the aforementioned materials is implanted in the body. A major problem that is often encountered after implantation of such a device in the body is inflammation of surrounding tissue.

Another major problem is the high incidence of infection.

A further problem that is often encountered after implantation of the medical device in the body is the formation of blood clots (thrombogenesis).

One additional problem that is also often encountered is the degradation, e.g., corrosion, of medical device leads and, thereby, premature failure of the device after implantation in the body.

Most medical devices are designed to be implanted in the body for an extended period of time. However, when a harsh biological response (or premature failure of the device) is encountered after implantation, it is often necessary to remove the device through a secondary surgical procedure, which can, and in many instances will, result in undesirable pain and discomfort to the patient, and possibly additional trauma to the adjacent tissue. In addition to the pain and discomfort, the patient must be subjected to an additional time consuming and complicated surgical procedure with the attendant risks of surgery.

There is thus a need to provide encasement structures that can be configured to encase for medical devices, which substantially reduce or eliminate the harsh biological responses associated with conventional implanted medical devices, including inflammation, infection and thrombogenesis.

It is therefore an object of the present invention to provide ECM sheet structures, which can be configured to encase a medical device and that substantially reduce or eliminate the harsh biological responses associated with conventional implanted medical devices, including inflammation, infection and thrombogenesis, when implanted in the body.

It is another object of the present invention to provide ECM sheet structures, which can be configured to encase a medical device, and effectively improve biological functions and/or promote modulated healing of adjacent tissue and the growth of new tissue when implanted in the body.

SUMMARY OF THE INVENTION

The present invention is directed to extracellular matrix (ECM) sheet structures, which can be configured to encase a medical device, and, when implanted in a body (i) substantially reduce or eliminate inflammation, infection and thrombogenesis, and (ii) induce modulated healing of damaged tissue and growth of new tissue when implanted in the body.

According to the invention, the medical device can comprise, without limitation, a pacemaker, defibrillator, synthetic heart valve, ventricular assist device, artificial heart, physiological sensor, catheter, and associated components, e.g., the electrical leads and lines associated therewith.

In some embodiments of the invention, the ECM sheet structures comprise an ECM composition comprising acellular ECM derived from a mammalian tissue source.

According to the invention, the mammalian tissue source can comprise, without limitation, small intestine submucosa (SIS), urinary bladder submucosa (UBS), stomach submucosa (SS), central nervous system tissue, epithelium of mesodermal origin, i.e. mesothelial tissue, gastrointestinal tissue, i.e. large and small intestine tissue, tissue surrounding growing bone, placental tissue, omentum tissue, cardiac tissue, e.g., pericardium and/or myocardium tissue, kidney tissue, pancreas tissue, lung tissue, and combinations thereof.

In a preferred embodiment of the invention, the acellular ECM is derived from mammalian submucosa tissue.

In a preferred embodiment, the ECM is decellularized and sterilized by a carbon dioxide (CO₂) process comprising the steps of (i) introducing the ECM into a reactor vessel, (ii) introducing CO₂ into the reactor vessel, (iii) pressurizing said reactor vessel at a pressure in the range of approximately 1000-3500 psi and at a temperature in the range of 25° -60° C., (iv) maintaining the ECM in contact with the CO₂ for a minimum processing time no less than 20 minutes, and (v) depressurizing the reactor pressure vessel at a depressurizing rate in the range of 725-1450 psi/min.

Preferably, the steps of introducing the CO₂ into the vessel interior space and maintaining the vessel pressure and temperature is performed contemporaneously during a maximum processing time no greater than 60 minutes.

In some embodiments of the invention, the ECM composition and, hence ECM sheet structures formed therefrom include at least one additional biologically active agent or composition, i.e. an agent that induces or modulates a physiological or biological process, or cellular activity, e.g., induces proliferation, and/or growth and/or regeneration of tissue.

In some embodiments of the invention, the biologically active agent comprises a growth factor.

According to the invention, upon deployment of a sheet structure of the invention in a subject, modulated healing and regeneration of tissue structures with site-specific structural and functional properties are effectuated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become apparent from the following and more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings, and in which like referenced characters generally refer to the same parts or elements throughout the views, and in which:

FIG. 1 is a perspective view of a biventricular (Bi-V) pacemaker;

FIG. 2 is a perspective view of one embodiment of an ECM sheet structure having the Bi-V pacemaker shown in FIG. 1 encased therein, in accordance with the invention;

FIG. 3 is a perspective view of an ECM sheet structure, illustrating a folded pre-lamination configuration of the sheet structure, in accordance with the invention;

FIG. 4 is a front, partial sectional plan view of the ECM sheet structure shown in FIG. 3, illustrating a laminated sheet structure end, in accordance with the invention; and

FIG. 5 is a front, partial sectional plan view of another embodiment of an ECM sheet structure, in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Before describing the present invention in detail, it is to be understood that this invention is not limited to particularly exemplified apparatus, systems, structures or methods as such may, of course, vary. Thus, although a number of apparatus, systems and methods similar or equivalent to those described herein can be used in the practice of the present invention, the preferred apparatus, systems, structures and methods are described herein.

It is also to be understood that, although the present invention is described and illustrated in connection with encased medical devices, the invention is not limited to encased medical devices. According to the invention, the ECM structures of the invention can also be employed to encase other devices, including, by way of example, a tracking device.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of the invention only and is not intended to be limiting.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the invention pertains.

Further, all publications, patents and patent applications cited herein, whether supra or infra, are hereby incorporated by reference in their entirety.

As used in this specification and the appended claims, the singular forms “a, “an” and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “an active” includes two or more such actives and the like.

Further, ranges can be expressed herein as from “about” or “approximately” one particular value, and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about” or “approximately”, it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” or “approximately” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “approximately 10” is also disclosed. It is also understood that when a value is disclosed that “less than or equal to” the value, “greater than or equal to the value” and possible ranges between values are also disclosed, as appropriately understood by the skilled artisan. For example, if the value “10” is disclosed then “less than or equal to 10” as well as “greater than or equal to 10” is also disclosed.

Definitions

The term “medical device”, as used herein, means and includes any device that is configured to modulate a physiological function of the body. The term “medical device” thus includes, without limitation, a pacemaker, defibrillator, synthetic heart valve, ventricular assist device, artificial heart, physiological sensor, catheter, and associated components thereof, including electrical leads and lines associated therewith.

The terms “extracellular matrix”, “ECM” and “ECM material” are used interchangeably herein and mean and include a collagen-rich substance that is found in between cells in mammalian tissue, and any material processed therefrom, e.g. decellularized ECM. According to the invention, the ECM material can be derived from a variety of mammalian tissue sources, including, without limitation, small intestine submucosa (SIS), urinary bladder submucosa (UBS), stomach submucosa (SS), central nervous system tissue, epithelium of mesodermal origin, i.e. mesothelial tissue, dermal tissue, subcutaneous tissue, gastrointestinal tissue, i.e. large and small intestine tissue, tissue surrounding growing bone, placental tissue, omentum tissue, cardiac tissue, e.g., pericardium and/or myocardium tissue, kidney tissue, pancreas tissue, lung tissue, and combinations thereof. The ECM can also comprise collagen from mammalian sources.

The terms “urinary bladder submucosa (UBS)”, “small intestine submucosa (SIS)” and “stomach submucosa (SS)” also mean and include any UBS and/or SIS and/or SS tissue that includes the tunica mucosa (which includes the transitional epithelial layer and the tunica propria), submucosal layer, one or more layers of muscularis, and adventitia (a loose connective tissue layer) associated therewith.

The ECM can also be derived from basement membrane of mammalian tissue/organs, including, without limitation, urinary basement membrane (UBM), liver basement membrane (LBM), and amnion, chorion, allograft pericardium, allograft acellular dermis, amniotic membrane, Wharton's jelly, and combinations thereof.

Additional sources of mammalian basement membrane include, without limitation, spleen, lymph nodes, salivary glands, prostate, pancreas and other secreting glands.

The ECM can also be derived from other sources, including, without limitation, collagen from plant sources and synthesized extracellular matrices, i.e. cell cultures.

The term “angiogenesis”, as used herein, means a physiologic process involving the growth of new blood vessels from pre-existing blood vessels.

The term “neovascularization”, as used herein, means and includes the formation of functional vascular networks that can be perfused by blood or blood components. Neovascularization includes angiogenesis, budding angiogenesis, intussuceptive angiogenesis, sprouting angiogenesis, therapeutic angiogenesis and vasculogenesis.

The terms “biologically active agent” and “biologically active composition” are used interchangeably herein and mean and include agent that induces or modulates a physiological or biological process, or cellular activity, e.g., induces proliferation, and/or growth and/or regeneration of tissue.

The terms “biologically active agent” and “biologically active composition” thus mean and include, without limitation, the following growth factors: platelet derived growth factor (PDGF), epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), transforming growth factor beta (TGF-beta), basic fibroblast growth factor (bFGF), vascular epithelial growth factor (VEGF), hepatocyte growth factor (HGF), insulin-like growth factor (IGF), nerve growth factor (NGF), platlet derived growth factor (PDGF), tumor necrosis factor alpha (TNF-alpha), and placental growth factor (PLGF).

The terms “biologically active agent” and “biologically active composition” also mean and include, without limitation, human embryonic stem cells, fetal cardiomyocytes, myofibroblasts, mesenchymal stem cells, autotransplated expanded cardiomyocytes, adipocytes, totipotent cells, pluripotent cells, blood stem cells, myoblasts, adult stem cells, bone marrow cells, mesenchymal cells, embryonic stem cells, parenchymal cells, epithelial cells, endothelial cells, mesothelial cells, fibroblasts, osteoblasts, chondrocytes, exogenous cells, endogenous cells, stern cells, hematopoietic stem cells, bone-marrow derived progenitor cells, myocardial cells, skeletal cells, fetal cells, undifferentiated cells, multi-potent progenitor cells, unipotent progenitor cells, monocytes, cardiac myoblasts, skeletal myoblasts, macrophages, capillary endothelial cells, xenogeneic cells, allogeneic cells, and post-natal stern cells.

The terms “biologically active agent” and “biologically active composition” also mean and include, without limitation, the following biologically active agents (referred to interchangeably herein as a “protein”, “peptide” and “polypeptide”): collagen (types I-V), proteoglycans, glycosaminoglycans (GAGS), glycoproteins, growth factors, cytokines, cell-surface associated proteins, cell adhesion molecules (CAM), angiogenic growth factors, endothelial ligands, matrikines, cadherins, immuoglobins, fibril collagens, non-fibrallar collagens, basement membrane collagens, multiplexins, small-leucine rich proteoglycans, decorins, biglycans, fibromodulins, keratocans, lumicans, epiphycans, heparin sulfate proteoglycans, perlecans, agrins, testicans, syndecans, glypicans, serglycins, selectins, lecticans, aggrecans, versicans, neurocans, brevicans, cytoplasmic domain-44 (CD-44), macrophage stimulating factors, amyloid precursor proteins, heparins, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate A, heparin sulfates, hyaluronic acids, fibronectins, tenascins, elastins, fibrillins, laminins, nidogen/enactins, fibulin I, fibulin II, integrins, transmembrane molecules, thrombospondins, osteopontins, and angiotensin converting enzymes (ACE).

The terms “pharmacological agent”, “active agent”, “drug” and “active agent formulation” are used interchangeably herein, and mean and include an agent, drug, compound, composition of matter or mixture thereof, including its formulation, which provides some therapeutic, often beneficial, effect. This includes any physiologically or pharmacologically active substance that produces a localized or systemic effect or effects in animals, including warm blooded mammals, humans and primates; avians; domestic household or farm animals, such as cats, dogs, sheep, goats, cattle, horses and pigs; laboratory animals, such as mice, rats and guinea pigs; fish; reptiles; zoo and wild animals; and the like.

The terms “pharmacological agent”, “active agent”, “drug” and “active agent formulation” thus mean and include, without limitation, antibiotics, anti-arrhythmic agents, anti-viral agents, analgesics, steroidal anti-inflammatories, non-steroidal anti-inflammatories, anti-neoplastics, anti-spasmodics, modulators of cell-extracellular matrix interactions, proteins, hormones, growth factors, matrix metalloproteinases (MMPS), enzymes and enzyme inhibitors, anticoagulants and/or antithrombotic agents, DNA, RNA, modified DNA and RNA, NSAIDs, inhibitors of DNA, RNA or protein synthesis, polypeptides, oligonucleotides, polynucleotides, nucleoproteins, compounds modulating cell migration, compounds modulating proliferation and growth of tissue, and vasodilating agents.

The terms “anti-inflammatory” and “anti-inflammatory agent” are also used interchangeably herein, and mean and include a “pharmacological agent” and/or “active agent formulation”, which, when a therapeutically effective amount is administered to a subject, prevents or treats bodily tissue inflammation, i.e. the protective tissue response to injury or destruction of tissues, which serves to destroy, dilute, or wall off both the injurious agent and the injured tissues.

Anti-inflammatory agents thus include, without limitation, alclofenac, alclometasone dipropionate, algestone acetonide, alpha amylase, amcinafal, amcinafide, amfenac sodium, amiprilose hydrochloride, anakinra, anirolac, anitrazafen, apazone, balsalazide disodium, bendazac, benoxaprofen, benzydamine hydrochloride, bromelains, broperamole, budesonide, carprofen, cicloprofen, cintazone, cliprofen, clobetasol propionate, clobetasone butyrate, clopirac, cloticasone propionate, cormethasone acetate, cortodoxone, decanoate, deflazacort, delatestryl, depo-testosterone, desonide, desoximetasone, dexamethasone dipropionate, diclofenac potassium, diclofenac sodium, diflorasone diacetate, diflumidone sodium, diflunisal, difluprednate, diftalone, dimethyl sulfoxide, drocinonide, endrysone, enlimomab, enolicam sodium, epirizole, etodolac, etofenamate, felbinac, fenamole, fenbufen, fenclofenac, fenclorac, fendosal, fenpipalone, fentiazac, flazalone, fluazacort, flufenamic acid, flumizole, flunisolide acetate, flunixin, flunixin meglumine, fluocortin butyl, fluorometholone acetate, fluquazone, flurbiprofen, fluretofen, fluticasone propionate, furaprofen, furobufen, halcinonide, halobetasol propionate, halopredone acetate, ibufenac, ibuprofen, ibuprofen aluminum, ibuprofen piconol, ilonidap, indomethacin, indomethacin sodium, indoprofen, indoxole, intrazole, isoflupredone acetate, isoxepac, isoxicam, ketoprofen, lofemizole hydrochloride, lomoxicam, loteprednol etabonate, meclofenamate sodium, meclofenamic acid, meclorisone dibutyrate, mefenamic acid, mesalamine, meseclazone, mesterolone, methandrostenolone, methenolone, methenolone acetate, methylprednisolone suleptanate, momiflumate, nabumetone, nandrolone, naproxen, naproxen sodium, naproxol, nimazone, olsalazine sodium, orgotein, orpanoxin, oxandrolane, oxaprozin, oxyphenbutazone, oxymetholone, paranyline hydrochloride, pentosan polysulfate sodium, phenbutazone sodium glycerate, pirfenidone, piroxicam, piroxicam cinnamate, piroxicam olamine, pirprofen, prednazate, prifelone, prodolic acid, proquazone, proxazole, proxazole citrate, rimexolone, romazarit, salcolex, salnacedin, salsalate, sanguinarium chloride, seclazone, sermetacin, stanozolol, sudoxicam, sulindac, suprofen, talmetacin, talniflumate, talosalate, tebufelone, tenidap, tenidap sodium, tenoxicam, tesicam, tesimide, testosterone, testosterone blends, tetrydamine, tiopinac, tixocortol pivalate, tolmetin, tolmetin sodium, triclonide, triflumidate, zidometacin, and zomepirac sodium.

The term “pharmacological composition”, as used herein, means and includes a composition comprising a “pharmacological agent” and/or a “biologically active agent” and/or any additional agent or component identified herein.

The term “therapeutically effective”, as used herein, means that the amount of the “pharmacological composition” and/or “pharmacological agent” and/or “biologically active agent” administered is of sufficient quantity to ameliorate one or more causes, symptoms, or sequelae of a disease or disorder. Such amelioration only requires a reduction or alteration, not necessarily elimination, of the cause, symptom, or sequelae of a disease or disorder.

The terms “prevent” and “preventing” are used interchangeably herein, and mean and include reducing the frequency or severity of a disease or condition. The term does not require an absolute preclusion of the disease or condition. Rather, this term includes decreasing the chance for disease occurrence.

The terms “treat” and “treatment” are used interchangeably herein, and mean and include medical management of a patient with the intent to cure, ameliorate, stabilize, or prevent a disease, pathological condition, or disorder. The terms include “active treatment”, i.e. treatment directed specifically toward the improvement of a disease, pathological condition, or disorder, and “causal treatment”, i.e. treatment directed toward removal of the cause of the associated disease, pathological condition, or disorder.

The terms “treat” and “treatment” further include “palliative treatment”, i.e. treatment designed for the relief of symptoms rather than the curing of the disease, pathological condition, or disorder, “preventative treatment”, i.e. treatment directed to minimizing or partially or completely inhibiting the development of the associated disease, pathological condition, or disorder, and “supportive treatment”, i.e. treatment employed to supplement another specific therapy directed toward the improvement of the associated disease, pathological condition, or disorder.

The terms “patient” and “subject” are used interchangeably herein, and mean and include warm blooded mammals, humans and primates; avians; domestic household or farm animals, such as cats, dogs, sheep, goats, cattle, horses and pigs; laboratory animals, such as mice, rats and guinea pigs; fish; reptiles; zoo and wild animals; and the like.

The term “comprise” and variations of the term, such as “comprising” and “comprises,” means “including, but not limited to” and is not intended to exclude, for example, other additives, components, integers or steps.

The following disclosure is provided to further explain in an enabling fashion the best modes of performing one or more embodiments of the present invention. The disclosure is further offered to enhance an understanding and appreciation for the inventive principles and advantages thereof, rather than to limit in any manner the invention. The invention is defined solely by the appended claims, including any amendments made during the pendency of this application, and all equivalents of those claims as issued.

As stated above, it is understood that, although the present invention is described and illustrated in connection with an encased medical device, the invention is not limited to encased medical devices. According to the invention, the ECM structures of the invention can also be employed to encase other devices, including, by way of example, a tracking device.

It is also understood that, although the present invention is described and illustrated in connection with a pacemaker, the invention is not limited to the noted medical device. Indeed, as stated above, the ECM encasement structures of the invention can also be employed to encase other medical devices, including, without limitation, a defibrillator, synthetic heart valve, ventricular assist device, artificial heart, physiological sensor, catheter, and associated components thereof, including electrical leads and lines associated therewith.

As discussed above, the present invention is directed to ECM sheet structures, which can be formed into encasement structures that are configured to encase devices; particularly, medical devices. According to the invention, the ECM sheet structures and, hence, encasement structures formed therewith can comprise various shapes and sizes to accommodate virtually all shapes and sizes of medical devices.

According to the invention, the encased medical device (and associated components) can comprise, without limitation, a pacemaker, defibrillator, synthetic heart valve, ventricular assist device, artificial heart, physiological sensor, catheter, and the electrical leads and lines associated therewith.

As indicated above, in some embodiments of the invention, the ECM sheet structures comprise an ECM composition comprising acellular ECM derived from a mammalian tissue source.

According to the invention, the ECM can be derived from various mammalian tissue sources and methods for preparing same, such as disclosed in U.S. Pat. Nos. 7,550,004, 7,244,444, 6,379,710, 6,358,284, 6,206,931, 5,733,337 and 4,902,508 and U.S. application Ser. No. 12/707,427; which are incorporated by reference herein in their entirety.

Suitable the mammalian tissue sources include, without limitation, small intestine submucosa (SIS), urinary bladder submucosa (UBS), stomach submucosa (SS), central nervous system tissue, epithelium of mesodermal origin, i.e. mesothelial tissue, gastrointestinal tissue, i.e. large and small intestine tissue, tissue surrounding growing bone, placental tissue, omentum tissue, cardiac tissue, e.g., pericardium and/or myocardium tissue, kidney tissue, pancreas tissue, lung tissue, and combinations thereof.

The ECM can also be derived from the same or different mammalian tissue sources, as disclosed in Co-Pending application Ser. Nos. 13/033,053 and 13/033,102; which are incorporated by reference herein.

In a preferred embodiment of the invention, the ECM is derived from mammalian submucosa tissue.

In a preferred embodiment, the ECM is decellularized and sterilized via a proprietary (i.e. Novasterilis®)) CO₂ sterilization process, as disclosed in U.S. application Ser. No. 13/480,205; which is expressly incorporated herein in their entirety.

As set forth in U.S. application Ser. No. 13/480,205, in one embodiment, the Novasterilis® CO₂ process comprises the steps of: (i) introducing the ECM into a reactor vessel, (ii) introducing CO₂ into the reactor vessel, (iii) pressurizing said reactor vessel at a pressure in the range of approximately 1000-3500 psi and at a temperature in the range of 25°-60° C., (iv) maintaining the ECM in contact with the CO₂ for a minimum processing time no less than 20 minutes, and (v) depressurizing the reactor pressure vessel at a depressurizing rate in the range of 725-1450 psi/min.

Preferably, the steps of introducing the CO₂ into the vessel interior space and maintaining the vessel pressure and temperature is performed contemporaneously during a maximum processing time no greater than 60 minutes.

As stated above, in some embodiments of the invention, the ECM composition(s) and, hence, ECM sheet structures formed therefrom, include at least one additional biologically active agent or composition, i.e. an agent that induces or modulates a physiological or biological process, or cellular activity, e.g., induces proliferation, and/or growth and/or regeneration of tissue.

Suitable biologically active agents include any of the aforementioned biologically active agents, including, without limitation, the aforementioned cells, proteins and growth factors.

In some embodiments, the ECM composition(s) and, hence, ECM sheet structures formed therefrom include at least one pharmacological agent or composition (or drug), i.e. an agent or composition that is capable of producing a desired biological effect in vivo, e.g., stimulation or suppression of apoptosis, stimulation or suppression of an immune response, etc.

Suitable pharmacological agents and compositions include any of the aforementioned agents, including, without limitation, antibiotics, anti-viral agents, analgesics, steroidal anti-inflammatories, non-steroidal anti-inflammatories, anti-neoplastics, anti-spasmodics, modulators of cell-extracellular matrix interactions, proteins, hormones, enzymes and enzyme inhibitors, anticoagulants and/or antithrombotic agents, DNA, RNA, modified DNA and RNA, NSAIDs, inhibitors of DNA, RNA or protein synthesis, polypeptides, oligonucleotides, polynucleotides, nucleoproteins, compounds modulating cell migration, compounds modulating proliferation and growth of tissue, and vasodilating agents.

According to the invention, the biologically active and pharmacological agents referenced herein can comprise any form. In some embodiments of the invention, the biologically active and pharmacological agents comprise microcapsules that provide delayed delivery of the agent contained therein.

According to the invention, upon deployment of an ECM sheet structure to or in a subject, modulated healing and regeneration of tissue structures with site-specific structural and functional properties are effectuated.

The phrase “modulated healing”, as used herein, and variants of this language generally refer to the modulation (e.g., alteration, delay, retardation, reduction, etc.) of a process involving different cascades or sequences of naturally occurring tissue repair in response to localized tissue damage or injury, substantially reducing their inflammatory effect. Modulated healing, as used herein, includes many different biologic processes, including epithelial growth, fibrin deposition, platelet activation and attachment, inhibition, proliferation and/or differentiation, connective fibrous tissue production and function, angiogenesis, and several stages of acute and/or chronic inflammation, and their interplay with each other.

For example, in some embodiments, the ECM compositions of the invention (and, hence, ECM sheet structures formed therefrom) are specifically formulated (or designed) to alter, delay, retard, reduce, and/or detain one or more of the phases associated with healing of damaged tissue, including, but not limited to, the inflammatory phase (e.g., platelet or fibrin deposition), and the proliferative phase.

In some embodiments, “modulated healing” refers to the ability of an ECM composition (and, hence, ECM sheet structures formed therefrom) to alter a substantial inflammatory phase (e.g., platelet or fibrin deposition) at the beginning of the tissue healing process. As used herein, the phrase “alter a substantial inflammatory phase” refers to the ability of an ECM composition to substantially reduce the inflammatory response at an injury site.

In such an instance, a minor amount of inflammation may ensue in response to tissue injury, but this level of inflammation response, e.g., platelet and/or fibrin deposition, is substantially reduced when compared to inflammation that takes place in the absence of an ECM composition of the invention.

For example, the ECM compositions discussed herein have been shown experimentally to delay or alter the inflammatory response associated with damaged tissue, as well as excessive formation of connective fibrous tissue following tissue damage or injury. The ECM compositions have also been shown experimentally to delay or reduce fibrin deposition and platelet attachment to a blood contact surface following tissue damage.

In some embodiments of the invention, “modulated healing” refers to the ability of an ECM composition of the invention (and, hence, ECM sheet structures formed therefrom) to induce host tissue proliferation, bioremodeling, including neovascularization, e.g., vasculogenesis, angiogenesis, and intussusception, and regeneration of tissue structures with site-specific structural and functional properties.

Accordingly, the ECM compositions of the invention and, hence, ECM sheet structures formed therefrom, provide an excellent bioabsorbable cellular interface suitable for use with a medical device or surgical instrument.

Referring now to FIG. 1, there is shown an exemplar implantable medical device; in this instance, a bi-ventricular (Bi-V) pacemaker 20, that can be encased by an ECM encasement structure of the invention. As is well known in the art and illustrated in FIG. 1, the Bi-V pacemaker 20 generally includes a pulse generator 21, electrical leads 22 a, 22 b, 22 c and lead tips or electrodes 24 a, 24 b, 24 c.

As is also well known in the art, the Bi-V pacemaker 20 is used to modulate the heart rate of a patient and prevent a life threatening heart dysfunction, e.g. arrhythmia.

The Bi-V pacemaker 20 is typically implanted transveniously in a patient, wherein two (2) electrical leads, i.e. leads 22 a, 22 b, are placed in a vein and guided to the right atrium and ventricle of the heart. The leads 22 a, 22 b are then attached to the heart muscle proximate the noted heart structures.

The third pacemaker lead, i.e., lead 22 c, is also guided through a vein to the coronary sinus (i.e. a small vein on the back of the heart) and attached to the heart to pace the left ventricle.

Referring now to FIG. 2, there is shown a first embodiment of an ECM sheet structure of the invention 10 a, having the medical device 20 encased therein.

As illustrated in FIG. 2, in the noted embodiment, the ECM sheet structure 10 a comprises a pocket or pouch 12 a having a cavity therein 13. The cavity 13 is sized and configured to receive and contain the medical device 20 therein.

In a preferred embodiment of the invention, the ECM sheet structure 10 a comprises at least one sheet member comprising an ECM composition of the invention. According to the invention, the ECM sheet structure 10 a and, hence, pouch 12 a formed therewith, can also include more than one sheet member.

Referring now to FIG. 3, there is shown a perspective view of the ECM sheet structure 10 a , showing a folded pre-lamination configuration of the ECM sheet structure 10 a. As illustrated in FIG. 3, in the noted embodiment, the ECM sheet structure 10 a comprises a single sheet member 14. According to the invention, to form a pouch 12 a that is configured to encase a medical device, such as medical device 20 shown in FIG. 1, the sheet member 14 is folded over and laminated on ends 18 a, 18 b, as illustrated in FIG. 4, and, in some embodiments, sides 16 a, 16 b.

Referring now to FIG. 5, there is shown another embodiment of an ECM sheet structure of the invention. As illustrated in FIG. 5, the ECM sheet structure 10 b comprises two (2) sheet members 15 a, 15 b. According to the invention, to form a pouch 12 b that is configured to encase a medical device, such as medical device 20 shown in FIG. 1, the sheet members 15 a, 15 b are laminated on ends 19 a, 19 b, 19 c, 19 d, and, in some embodiments, at least sides 17 a, 17 b.

According to the invention, the ends 18 a, 18 b, 19 a, 19 b, 19 c, 19 d and sides 16 a, 16 b, 17 a, 17 b of the sheet members 14, 15 a, 15 b of the invention can be laminated by various conventional means, such as stitching, including ECM stitches, stapled, adhesives. The ends 18 a, 18 b, 19 a, 19 b, 19 c, 19 d and sides 16 a, 16 b, 17 a, 17 b of the sheet members 14, 15 a, 15 b can also be laminated via microneedles and/or microneedle structures, such as disclosed in Co-Pending application Ser. No. 13/686,131.

Without departing from the spirit and scope of this invention, one of ordinary skill can make various changes and modifications to the invention to adapt it to various usages and conditions. As such, these changes and modifications are properly, equitably, and intended to be, within the full range of equivalence of any subsequently proffered claims. 

What is claimed is:
 1. A sheet structure, comprising: a sheet member comprising an extracellular matrix (ECM) composition comprising sterilized and decellularized ECM derived from a mammalian submucosa tissue, said ECM being sterilized and decellularized by a process comprising (i) introducing said ECM into a reactor vessel, (ii) introducing carbon dioxide (CO₂) into said reactor vessel, (iii) pressurizing said reactor vessel at a pressure in the range of approximately 1000-3500 psi and at a temperature in the range of 25°-60° C., (iv) maintaining said ECM in contact with said CO2 for a minimum processing time no less than 20 minutes, and (v) depressurizing said reactor pressure vessel at a depressurizing rate in the range of 725-1450 psi/min, wherein said ECM comprises a dry weight DNA content of less than 1 μg/g and exhibits at least 96% decellularization, and wherein said ECM exhibits an altered collagen and fibronectin structure, said sheet member being adapted to modulate inflammation of damaged biological tissue and induce in vivo cell proliferation, remodeling of said damaged biological tissue, and regeneration of new tissue and tissue structures with site-specific structural and functional properties, when said sheet member is delivered to said damaged biological tissue.
 2. The sheet structure of claim 1, wherein said sheet structure comprises a post-processing dry weight transforming growth factor beta (TGF-β) content greater than 2.8 pg/mg and basic fibroblast growth factor (bFGF) content greater than 19 pg/mg.
 3. The sheet structure of claim 1, wherein said sheet structure comprises a pouch structure having an internal region configured to receive a medical device therein,
 4. The encasement structure of claim 1, wherein said bioremodelable ECM composition further includes a growth factor comprising basic fibroblast growth factor (bFGF). 